1. Field of the Invention
The present invention relates to a brush charging device for use in an image forming apparatus and to a method for manufacturing the brush charging device.
2. Description of the Related Art
In recent years, a contact charging device such as a charging brush has been employed in place of a corona charger. The charging brush does not produce a large amount of ozone. However, when such charging brush is used for copying machines and printers especially electronic photo-copying apparatus employing a reversed developing method, a number of lines are produced on the printing surface during the printing of half tones as if drawn by a paint brush. In an electronic photo-copying apparatus employing the reversed developing based on negative charges, such lines appear as white lines. This means that the surface potential of the photo-sensitive drum is locally higher on the negative side. These uneven lines are peculiar to the brush, especially remarkable in a fixed type conductive brush. Furthermore, a charging brush whose surface has substantially the same curvature as that of the photo-sensitive drum surface should be used so that the tip of the brush uniformly contacts the photo-sensitive drum surface as disclosed in Japanese Patent Disclosure (kokai) No. 210862/88. But no appropriate method has been known for mass-producing such brushes.